Typewriter ribbons having correction coating and method of making

ABSTRACT

The invention provides typewriting ribbons which comprise on a single, homogeneous support consisting of a synthetic polymer film a writing, inked part and a part suitable for correcting typing mistakes coated with a white, hiding composition. The support, preferably made of a polyester resin or of polypropylene, is preferably coated with a thin layer essentially consisting of a vinylidenic polymer. The hiding composition for correction contains essentially 75-98 percent b.w. of a pigment which is titanium bioxide having an oil index of between 30 and 60, 0.5-10 percent b.w. of a binder which is a rubber-like resin having a molecular weight over 2,000 and soluble in organic solvents, little percentages of a wetting agent.

United States Patent Sala et al. May 23, 1972 54] TYPEWRITER RIBBONS HAVING 3,114,447 12/1963 Wolowitz ..117 2 3,141,539 7/1964 Wolowitz..... ggg g g AND M 0 0 MA NG 3,328,190 6/1967 [72] Inventors: Sergio Sala; Ambrosio Cuneo, both of via 3,459,127 8/1969 Barouh .1l7/36.l

g g i y g g Primary ExaminerMurray Katz roos rasse, tv1 e am me, er- Atmmey .roren &McGeady many [22] Filed: Jan. 23, 1969 ABSTRACT 2 App] 793 27 The invention provides typewriting ribbons which comprise on a single, homogeneous support consisting of a synthetic polymer film a writing, inked part and a part suitable for corl Foreign Application Priority Data recting typing mistakes coated with a white, hiding composition. The support, preferably made of a polyester resin or of 1968 italy "2 N68 polypropylene, is preferably coated with a thin layer essen- Dec. 14, con ng fa ny en c p y er The c pos tion for correction contains essentially 75-98 percent b.w. of a [52] US. Cl. ..117/2 TC, 1 l7/36.4, 1 17/44, pigment which is titanium bioxide having an oil index f 1 l7/l 260/41 C between 30 and 60, 0.5-10 percent b.w. ofa binder which is a [51] Int.Cl ..B4lm 5/10 rubber-like resin having a molecular weight over 2,000 and [58] Field of Search ..117/2 TC, 36.l,36.4; 197/172 soluble in organic solvents, little percentages of a wetting agent. [56] References Cited 21 Claims, 3 Drawing Figures UNITED STATES PATENTS 3,034,9l8 5/l962 Cook et al. l l7/36.4

TYPEWRITER RIBBONS HAVING CORRECTION COATING AND METHOD OF MAKING The invention refers to typewriting ribbons which comprise, on a carrier sheet, a composition for correcting typing errors and, more particularly, it refers to typewriting ribbons with half of each ribbon being inked and the second half being covered with a layer of a composition for making corrections The correction of the wrong typewritten letters is efi'ect'ed by switching the typewriting ribbon from the inked part to the correcting part and then retyping on the error the same letter; in this way a portion of the correcting composition, having the form of the typed letter is detached and adhers to the sheet of paper. The correct letter is then typed, in the usual way, on this layer of the correcting composition, using the inked ribbon.

Typewriting ribbons made up, partly of an inked ribbon and partly of a correcting ribbon for cancelling the typing errors, are already known through the U.S. Pats. Nos. 3,114,447 and 3,143,200. In these ribbons, on inked fabric ribbons, for instance of natural silk, used in the usual manner, a second carrier sheet for the correcting composition is applied, and,

between the two coats (the inked coat and the correcting coat) a separating stripe is eventually inserted to stop the transfer of the oily substances containing the dissolved dyes into the correcting composition.

These known typewriting ribbons with correcting coats have nevertheless disadvantages which make them unsuitable for practical use. For instance, the different materials used for the inked ribbon and for the carrier of the correcting coat, do not generally have the same elasticity, this is why these well known typewriting ribbons, after being used for a short period of time become more wrinkled until they become unusable. Furthermore, the transfer of the portion of the correcting composition (which should faithfully follow the outlines of the typewritten letter) from the correcting coat to the typewriting paper, take place in an unsatisfactory manner considering that the carrier in the assembly consists of: a relatively thick fabric ribbon, of an adhesive coating and of the carrier strip forthe correcting composition. A further disadvantage of the well known typewriting ribbons, suitable for correcting typing errors, lies in the fact that they have a low resistance to creasing so that, after several runs of the ribbon through the typewriter, the correcting composition is more or less detached from the ribbon itself.

It is, therefore, the scope of the invention herewith to produce typewriting ribbons highly elastic and resistant to wrinkling and to friction, which, for instance, for one half of the width, are coated with a correcting composition for correcting typewriting errors. In these typewriting ribbons the correcting composition must remain efficient for as long as the typewriting coating, and also after many runs through the typewriter, it must neither detach or scrape off.

The above mentioned objects have been achieved by us by the use of a single carrier film made of a synthetic polymer capable of anchoring securely both the ink and the correcting composition and by preparing new correcting compositions, which, unlike those hitherto known, form highly elastic coatings which can resist friction and are capable of adhering very firmly to the particular carriers of the invention made of synthetic, non-porous material.

The main advantage of the typewriting ribbon in accordance with the invention herewith, which contemporaneously serve the purpose of both typing and correcting, consists of the fact that two different coatings on one single homogeneous carrier, and, therefore, the complicated and scarcely stable, in time, products of lamination of two coatings of carrier, as different from one another as fabrics and sheets of synthetic material of the types described in the above mentioned U.S. Pats, are no longer necessary. As the sheets of synthetic materials, unlike the fabric ribbons, may be produced in wide strips, there is also the possibility of applying, in one single phase, by means of suitable machines, in wide strips, both the writing coating and the correcting coating.

Furthermore, by doing away with the use of the costly natural silk ribbons, the possibility of keeping the production cos very low, should be considered.

The homogeneous carrier coating, according to the invention is made of a film of resistant synthetic material, preferably a polyester or polypropylene on which a coat of polymer has been applied. This under-coat of vinylidenic polymer improves the adhesion to the carrier of the inked coating and of the correcting composition coating.

As already mentioned the well known correcting compositions are little suitable for application on sheets of synthetic material, as they produce relatively inelastic coatings which present little adhesivity to the sheets of synthetic material.

The cause of this low adhesivity is to be found in the fact that the coatings produced with the well known formulations, have considerable contents of undissolved binding substances, but only suspended or swollen, such as metallic soaps or waxes, which are useful for bringing about the possibility of typing over the corrected spaces.

We have now found that an advantageous solution of the problem is obtained by using, instead of the white pigments of tita-nium bioxide, proposed up to now, as for instance KRONOS RN 56, having an oil index of about 20, titanium bioxide pigments which have an oil index about double.

With the term oil index it is generally meant an index for the amount of oil (generally linseed oil) needed to completely wet the pigment particles.

The typewriting ribbons in accordance with the invention, also suitable for correcting typing errors, made of a carrier coating and of a microporous correcting coating adhering to the carrier, containing a pigment and a binding agent, but deprived of components liquid under 50 C., are characterized by the fact that the carrier is made of a sheet of synthetic material with a substantially waterproof surface, preferably provided with an under-coat of vinylidenic polymer, and that the correcting composition, applied in a coat corresponding to about l0-l5g/m of dry substance, contains: as a pigment, about 75-98 percent, by weight, of titanium bioxide with an oil index between 30 and 60; as a binder, about 05-10 percent, by weight, of at least one rubber-like resin having a molecular weight of at least 2,000, essentially completely soluble in the organic solvents, producing a low viscosity solution, and 0.5-2 percent by weight of a wetting agent.

For the purpose of making the correcting coat still more superficially resistant to friction, it is preferred to add to the composition 1-10 percent, by weight, of microtalcum.

The pigments used in accordance with the invention are available in commerce: let us mention, for instance, the pigment produced by the Titangesellschaft m.b.H.(Leverkusen), under the trade name of KRONOS RN 44; the high oil index is the result of a special process applied to the surface, i.e. the modification of the single crystals of titanium bioxide. For the use in the compositions in accordance with the invention, together with the oil index, contrarily to what occurs in applications by the lacquer industries, the hiding power of the pigment thus treated is considerably increased, so that the thickness of the coat of correcting composition can be maintained by about 20-40 percent under that of the well known correcting sheets.

Summing up, by using pigments with a high oil index, it is possible to achieve the following advantages:

l. The percentage of binder, purely suspended or swollen, may be lowered and therefore, the percentage content of dissolved binder may be increased, without causing the adherence of the coating to become so high as to damage its transfer capacity, i.e. the coating remains microporous;

2. because of the relatively high percentage of the pigment, the thickness of the coat may be reduced so that the coating becomes more elastic and more resistant to the formation of creases;

3. the capacity of the corrected parts to receive fresh typing is increased, as the pigments with a higher oil index having a larger surface, better absorb the inks;

4. the capacity to receive fresh typing is also increased because of the lesser thickness of the hiding coat. The correcting ribbon can adhere better to the sheet to be corrected.

It is evident that the above mentioned advantages due to the use of pigments with a higher oil index, may be achieved with good results also when as carrier sheet for the correcting coating, paper is being used as in the past.

Resins having a rubber-like consistency, having a molecular weight of over 2,000, used as binders, in accordance with this invention, must essentially be completely soluble in the organic solvents used in the preparation of the correcting composition, and capable of producing, together with these, practically low viscosity solutions.

The rubber that may be used in accordance with this invention are for instance: polyvinylisobutylether, polychloroprene, polyethylene chlorosulphonate, butyl rubber, polyisobutylene, polyacrylic resins, polystyrene, styrene copolymers.

Methylenchloride, ethylene trichloride, toluene, ethyl acetate and others are suitable as solvents.

Lecithin and fatty acids of a high molecular weight and with an appropriate number of carbon atoms above l8, such as, for instance, beenic acid, are, in accordance with this invention, preferably used as wetting agents.

The correcting compositions in accordance with the invention, may moreover contain about 05-10 percent, by weight, of at least one hard resin soluble in the organic solvent used, as for instance, a phenolic resin modified with colophony, a ketonic resin, chlorinated rubber, cyclized rubber or polyvinylic resins.

Cellulose derivatives such as ethyl cellulose or cellulose butyrate-acetate, are the preferred hard resins.

To advantage, the correcting compositions may also contain about ll percent, by weight of a hard wax, of a hard parafin or a polyvalent soap which is insoluble or only partly soluble in the organic solvent. Examples of such compounds are hard ceresine, purified montan wax, hydrocarbon waxes. Among the polyvalent metallic soaps those particularly preferred are aluminum soaps, such as aluminum stearate.

A particularly advantageous result is obtained by adding to the correcting composition up to about percent, by weight, of an polyisobutylene having an average molecular weight of about 3,000, as it explicates the function of a plasticizer and enhances the capacity of the correcting composition, when applied to the typing paper, to receive fresh typing without favoring the oozing through of the ink.

Lastly, it is possible to add advantageously to the correcting regular intervals apart. In this manner a coat of ink, the thickness of which is determined by means of a proportionating cylinder, is applied by the projecting sections of the cylinder on the corresponding surface of the film, whereas the surface of the film corresponding with the grooves will remain bare.

Particularly suitable inks are self-regenerative inks of the type described in Italian Patent No. 810,175.

The films then runs through a hot air tunnel in which the temperature is progressively raised from 40 to 60 C.

The length of the tunnel is regulated in function of the characteristics of the ink in such a manner that the inked strips are perfectly dry when leaving the tunnel.

The carrier film is then run through a device identical to the first one but in which the position of the grooves on the inking cylinder is inverted in relation to that of the cylinder of the first device, in such a way that this time the suspension is applied on the strips of the carrier which have remained bare in the first treatment. This second device is used for applying the hiding white paste.

The film, having regular strips of the desired width alternatively coated with ink and with hiding composition, is then run through yet another drying tunnel and then through a cutting machine where the single typewriting ribbons, to the desired width, are obtained.

composition an adsorbent medium preferably a derivative of v montmorillonite, as for instance the product of the reaction of quaternary alkyl-ammonium bases with the montmorillonite. These adsorbent media enhance the capacity of the correcting compositions to stop the bleeding of the ink from the letters typed in error and which are under the hiding coat.

The correcting compositions in accordance with the invention, may be obtained in a simple manner, by thoroughly mixing, for example in a ball mill, the various components of the correcting composition with organic solvents such as trichloroethylene, ethylene or methylene chloride, toluene, ethyl acetate or even mixtures of such solvents; the mixture is then diluted with the organic solvent to a fluid consistency and applied in the desired thickness onto the carrier.

We have also found that in order to make the new ribbons in accordance with the invention, it is necessary to adopt a special process. In substance, it is necessary, contrary to what is being done in the case of ordinary typewriting ribbons, to apply, in two successive stages the ink and the white paste, drying the coating first applied under given critical temperature conditions, before applying the second coating. Such a process when applied to ordinary typewriting ribbons leads to useless products.

More precisely, the process of the invention consists in running a reel of carrier film covered with an adhesive undercoat, over an inking roller with peripheral grooves, ofa circular crossection, parallel to each other, of a set width and at Should one prefer to make single ribbons directly, in widths from 8 to 40mm, the inking cylinders will obviously have only one projecting part and only one groove of the width of the inked strip and of the hiding composition strip, of the ribbon being produced.

The apparatus required for carrying out the process of the invention is schematically shown in the enclosed drawings:

' In FIG. 1, 1 represents the inking cylinder, 2 is the proportionating cylinder and 3 the cylinder that dips into chamber 4 containing the ink. Film 5, after having been guided by appropriate rollers in contact with roller 1, is run through, always by means of appropriate rollers, a hot air tunnel which is not shown. It then enters a device identical to the one described, which is also not shown, where the white hiding paste is applied and dried.

FIG. 2 is a side view of an inking cylinder for multiple ribbons which will subsequently be cut into single ribbons by an appropriate cutting machine, while FIG. 3 is a side view of an inking cylinder for making single ribbons.

In preference the carrier films are to be 10-25 ,u. thick which is equivalent to 18-70 g/m The under-coating required to make both the ink and the white correcting paste adhere to the carrier, is preferably made up of polyvinylidene chloride.

This under-coating is applied in the form of a suspension in a suitable solvent, preferably acetone and/or methyl-ethylketone, containing small percentages of a plasticizer and of a stabilizer of the suspension in thicknesses equivalent to 6-20 g/ 2.

The suspensions applied have solid concentrations of 10-15 percent.

For illustrative but not restrictive purposes we now refer some examples of what can be achieved in accordance with the invention.

EXAMPLE 1 A suspension containing polyvinylidene chloride (F/220 type of Union CARBIDE) 98.9 pp triphenylphosphate 1.0 pp phosphoric acid .1 pp acetone 800 pp was applied on a Mylar (Registered Trade Mark) film 50 cm wide and weighing 50 g/m After drying, an under-coating of 15 g/m thick, of the above mentioned composition, remains on the carrier film.

The film thus treated is run over an inking cylinder having alternating projections and grooves 6.5mm wide, in such a way that strips of ink 6.5mm wide alternate with bare strips of the film also 65mm wide.

The self-regenerative ink applied has the following composition:

Cellulose butyrate-acetate 171/2 150 pp Sperm oil 35 pp Ricinoleic acid 30 pp Colza Oil 30 pp Oleic acid 5 pp Ultramarin blue 40 pp Carbon black 30 pp Acetone and methyl-ethyl ketone 400 pp On leaving the inking roller the film is run through a tunnel in which the air is heated to 45 C. at the inlet end and then progressively up to 60 C. at the outlet end. Perfectly dried it is run through a device which is identical to the first one, the inking roller of which, has the position of the projecting parts and of the grooves inverted in relation to those of the first device.

On the strips thus remaining bare, a hiding paste previously prepared, and having the following composition, is applied:

parts by weight of a 10 percent solution of polyvinylisobutyl-ether in trichloroethylene,

25 parts by weight of a 5 percent solution of ethyl-cellulose in trichloroethylene,

1 part by weight of lecithin (very pure, free of oil),

50 parts by weight of titanium bioxide having an oil index of about 40 (KRONOS RN 44) produced by Titangesellschaft mbH Leverkusen,

and 70 parts by weight of trichloroethylene.

The film, now completely covered, runs through another air tunnel where it is being dried in mild conditions, i.e. at temperatures not exceeding 60 C. and then through a cutting machine where it is cut into 13mm ribbons.

Both the inked coat and the white correcting coat have a uniform thickness of l5,u..

In this manner a highly elastic ribbon resistant to wrinkles is obtained which also serves for correcting typing errors; after numerous runs through the typewriter the correcting composition will not drop off.

EXAMPLE 2 A typewriting ribbon has been partially coated following the process if Example 1 with a correcting composition consisting of:

10 parts by weight of polyvinylisobutylether 1 part by weight of cyclized rubber (Alpex) 1 part by weight oflecithin parts by weight of titanium bioxide (RN 44) and 80 parts by weight of trichloroethylene.

EXAMPLE 3 A typewriting ribbon has been partially coated, following the process of Example 1, with a correcting composition consisting of 20 parts, by weight, of a 2 percent solution of butyl rubber in trichloroethylene; 2 parts by weight of cellulose acetate butyrate; 1 part by weight of lecithin, 50 parts by weight of titanium bioxide (RN 44) and 80 parts by weight of trichloroethylene.

EXAMPLE 4 EXAMPLE 5 A typewriting ribbon has been partially coated, following the process of Example 1 with a correcting composition comprising 10 parts by weight of a 10 percent solution of polyvinylisobutylether in trichloroethylene; 25 parts by weight of a 5% solution of ethylcellulose in trichloroethylene; 5 parts by weight of Al monobehenate; 1 part by weight of lecithin; 3 parts by weight of Bentone; 50 parts by weight of titanium bioxide (RN 44) and parts by weight of trichloroethylene.

In all the cases, as in Example 1, elastic ribbons for correcting typing errors, resistant to wrinkling and abrasion, were obtained.

We claim 1. A typewriting ribbon having a coating thereon for the correction of typing errors and comprising a support member formed of a synthetic polymer film having a substantially im permeable surface, an undercoat of vinylidenic polymer being formed on the substantially impermeable surface of said support member, a coating of an ink composition deposited on a portion of the transverse surface of said undercoat and a coating of a microporous correcting composition deposited on the remainder of the transverse surface of said undercoat for providing co-extending continuous bands of inking and correcting compositions thereon, and said coating of a correcting composition having a thickness corresponding to 10 15g/m of dry substance and comprising as a pigment -98 percent, by weight, of titanium bioxide having an oil index of between 30 and 60, as a binder about 05-10 percent, by weight, of at least one rubber-like resin having a molecular weight over 2000 and being substantially completely soluble in organic solvents, and a wetting agent of about 0.5-2 percent by weight.

2. A typewriting ribbon, as set forth in claim 1, wherein said undercoat of vinylidenic polymer consists essentially of polyvinylidene chloride.

3. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises 05-10 percent, by weight, of at least one hard resin soluble in organic solvents.

4. A typewriting ribbon, as set forth in claim 3, wherein said hard resin is a cellulose derivative.

5. A typewriting ribbon, as set forth in claim 1, wherein said wetting agent in said correcting composition consists of one of lecithin and a fatty acid of a high molecular weight.

6. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 1-1 0 percent, by weight, of one of a hard wax, a hard paraffin, and a hard polyvalent soap, which are at most only partly soluble inorganic solvents.

7. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 5 percent by weight, of polyisobutylene having an average molecular weight of about 3,000.

8. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises a derivative of montmorillonite acting as an absorbent medium.

9. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 1-10 percent by weight of microtalcum.

10. A typewriting ribbon, as set forth in claim 1, wherein said support member is formed of a sheet of one of polyester and polypropylene.

11. A process for manufacturing typewriter ribbons used for typing ink characters and for correcting typing errors by applying a covering composition, comprising covering the transverse surface of a synthetic polymer film support member with an undercoat of a vinylidenic polymer, drying the undercoat, applying a coating of ink to a portion of the transverse undercoated surface of the support member in at least one longitudinally extending strip leaving the remainder of the transverse surface uncoated, drying the ink coating, coating the remainder of the transverse surface of the support member with a typing error covering composition containing titanium bioxide pigments having an oil index between 30 and 60, and drying the covering composition.

12. A process, as set forth in claim 11, wherein using a 10-15 percent suspension in acetone of 98.9 parts of polyvinylidene chloride and the balance to form 100 parts consisting of small percentages of a plasticizer and of a stabilizer for forming the undercoat.

13. A process, as set forth in claim 1 1, wherein using a selfregenerative ink for coating the undercoated support member 'with the ink in the form of a suspension in one of acetone and methyl-ethyl-ketone.

14. A process, as set forth in claim 13, wherein using as the correcting composition a substance comprising as a pigment 75-98 percent, by weight of titanium bioxide, as a binder about 1.5-10 percent by weight of at least one rubber-like resin having a molecular weight over 2,000 and being substantially completely soluble in organic solvents, and a wetting agent of about 0.5-2 percent by weight, and regulating the thickness of the coating of the correcting composition whereby it corresponds to about 10-1 Sg/m of dry substance.

15. A process, as set forth in claim 14, wherein the correcting composition comprises about 0.5-10 percent, by weight of a hard resin soluble in organic solvents.

16. A process, as set forth in claim 15, wherein the hard resin is a cellulose derivative.

17. A process, as set forth in claim 15, wherein the wetting agent in the correcting composition consists of one of lecithin and a fatty acid having a high molecular weight.

18. A process, as set forth in claim 15, wherein the correcting composition comprises about l-lO percent by weight of one of a hard wax, a hard paraffin, and a polyvalent metallic salt which are at most only partly soluble in organic solvents.

19. A process, as set forth in claim 15, wherein the correcting composition comprises about 5 percent by weight of a polyisobutylene having an average molecular weight of about 3,000.

20. A process, as set forth in claim 15, wherein the correcting composition comprises a derivative of montmorillonite acting as an absorbent medium.

21. A process, as set forth in claim 15, wherein said correcting composition comprises about 5-10 percent by weight of microtalcum. 

2. A typewriting ribbon, as set forth in claim 1, wherein said undercoat of vinylidenic polymer consists essentially of polyvinylidene chloride.
 3. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises 0.5-10 percent, by weight, of at least one hard resin soluble in organic solvents.
 4. A typewriting ribbon, as set forth in claim 3, wherein said hard resin is a cellulose derivative.
 5. A typewriting ribbon, as set forth in claim 1, wherein said wetTing agent in said correcting composition consists of one of lecithin and a fatty acid of a high molecular weight.
 6. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 1-10 percent, by weight, of one of a hard wax, a hard paraffin, and a hard polyvalent soap, which are at most only partly soluble in organic solvents.
 7. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 5 percent by weight, of polyisobutylene having an average molecular weight of about 3,
 000. 8. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises a derivative of montmorillonite acting as an absorbent medium.
 9. A typewriting ribbon, as set forth in claim 1, wherein said correcting composition comprises about 1-10 percent by weight of microtalcum.
 10. A typewriting ribbon, as set forth in claim 1, wherein said support member is formed of a sheet of one of polyester and polypropylene.
 11. A process for manufacturing typewriter ribbons used for typing ink characters and for correcting typing errors by applying a covering composition, comprising covering the transverse surface of a synthetic polymer film support member with an undercoat of a vinylidenic polymer, drying the undercoat, applying a coating of ink to a portion of the transverse undercoated surface of the support member in at least one longitudinally extending strip leaving the remainder of the transverse surface uncoated, drying the ink coating, coating the remainder of the transverse surface of the support member with a typing error covering composition containing titanium bioxide pigments having an oil index between 30 and 60, and drying the covering composition.
 12. A process, as set forth in claim 11, wherein using a 10-15 percent suspension in acetone of 98.9 parts of polyvinylidene chloride and the balance to form 100 parts consisting of small percentages of a plasticizer and of a stabilizer for forming the undercoat.
 13. A process, as set forth in claim 11, wherein using a self-regenerative ink for coating the undercoated support member with the ink in the form of a suspension in one of acetone and methyl-ethyl-ketone.
 14. A process, as set forth in claim 13, wherein using as the correcting composition a substance comprising as a pigment 75-98 percent, by weight of titanium bioxide, as a binder about 1.5-10 percent by weight of at least one rubber-like resin having a molecular weight over 2,000 and being substantially completely soluble in organic solvents, and a wetting agent of about 0.5-2 percent by weight, and regulating the thickness of the coating of the correcting composition whereby it corresponds to about 10-15g/m2 of dry substance.
 15. A process, as set forth in claim 14, wherein the correcting composition comprises about 0.5-10 percent, by weight of a hard resin soluble in organic solvents.
 16. A process, as set forth in claim 15, wherein the hard resin is a cellulose derivative.
 17. A process, as set forth in claim 15, wherein the wetting agent in the correcting composition consists of one of lecithin and a fatty acid having a high molecular weight.
 18. A process, as set forth in claim 15, wherein the correcting composition comprises about 1-10 percent by weight of one of a hard wax, a hard paraffin, and a polyvalent metallic salt which are at most only partly soluble in organic solvents.
 19. A process, as set forth in claim 15, wherein the correcting composition comprises about 5 percent by weight of a polyisobutylene having an average molecular weight of about 3,
 000. 20. A process, as set forth in claim 15, wherein the correcting composition comprises a derivative of montmorillonite acting as an absorbent medium.
 21. A process, as set forth in claim 15, wherein said correcting composition comprises about 5-10 percent by weight of microtalcum. 